The Herpesviridae are common infectious agents. For example, the herpes simplex viruses (HSV) are infectious agents which cause a number of diseases. The entry of HSV in the target cells begins with binding of the virus to the cell surface heparan sulfate proteoglycans (1, 2). Several experimental lines of evidence prove the existence and importance of this binding. First, in HEp-2 cells, enzymatic digestion of cell surface heparan sulfate proteoglycans (HSP) with heparitinase and heparinase decreases binding of HSV-1 and HSV-2 to the cells, as well as plaque formation (1). Second, heparin, heparan sulfate, cationic aminoglycosides, poly-L-lysine and heparin-binding protein PF4 decrease binding and infectivity of HSV in several experimental systems (1-8). All these compounds can inhibit virus association with the cell surface either by binding to the cellular HSP, or by binding to the viral proteins capable of interaction with HSP. Third, purified HSV and its glycoproteins gB and gC bind to heparin-Sepharose beads (9). The gB is an "indispensable" envelope glycoprotein which is involved in penetration of virus into target cell, while gC, although a "dispensable" glycoprotein, plays an important role in both absorption and penetration of virus (10-14). A similar role is played by the gB and gC homologs in another member of herpes family: human cytomegalovirus (15,16). Recently, it was suggested that HSV can utilize a high-affinity receptor for a heparin-binding growth factor bFGF, as a "portal for cellular entry" (17, 18). However, subsequent studies indicated that high affinity bFGF receptor is not necessarily involved in HSV binding (19-21). These contradictory results may be reconciled by the discovery that interaction of bFGF with cell surface HSP or soluble heparin is a necessary step in the process of bFGF binding to high affinity receptor (22-24). The latter findings may explain why under certain experimental conditions, bFGF may inhibit viral adsorption and infectivity without direct involvement of bFGF high affinity receptor.